The gastrointestinal epithelium functions as a dynamic permeability barrier that separates luminal contents from underlying tissue compartments and is vital in maintaining mucosal homeostasis. Pathologic processes such as inflammatory bowel disease and ischemia induce epithelial injury and mucosal wounds that result in barrier disruption. In response to injury, intestinal epithelial cells (IECs) migrate as a cohesive sheet to rapidly cover denuded surfaces, close wounds and re-establish the critical epithelia barrier in a process termed restitution. Epithelial cell migration is critically dependent on actin cytoskeletal restructuring, directional polarization of cells into the wound and dynamic focal cell-matrix adhesion turnover. The long term goals of this proposal are to define mechanisms by which the intestinal epithelium migrates in response to injury and inflammation to efficiently reseal mucosal barrier defects. We recently determined that a multifunctional membrane associated and actin binding protein, Annexin 2 (AnxA2) and a secreted regulator of Wnt signaling, Dickkopf-1 (Dkk-1), play critical roles in controlling IEC migration and restitution. Thus our aims in this proposal are to define the mechanisms by which AnxA2 and Dkk-1 regulate IEC motility and wound closure. These studies will not only advance our understanding of AnxA2 and Dkk-1 function in the intestine, but will also aid in the development of new therapeutic strategies aimed at facilitating mucosal barrier recovery. PUBLIC HEALTH RELEVANCE: The gastrointestinal epithelium functions as an important barrier that separates luminal contents from underlying tissue compartments. Disruption of the epithelial barrier in inflammatory bowel diseases and ischemia result in fluid & electrolyte loss and exposure of tissues to luminal antigens and pathogens. To rapidly reseal such wounds, epithelial cells migrate in a process termed restitution. Our studies are aimed at understanding mechanisms by which the intestinal epithelium migrates to rapidly cover denuded surfaces and reseal wounds. We recently determined that two proteins, annexin-2 and Dickkopf-1 control intestinal epithelial cell migration and wound recovery. The proposed studies will analyze the mechanisms by which these proteins regulate intestinal epithelial wound recovery. These investigations will not only define the mechanisms by which these proteins regulate wound resealing, but will also provide new ideas to identify therapeutic agents aimed at promoting intestinal epithelial wound closure and mucosal barrier recovery.